21247065 has 48 divisors (see below), whose sum is σ = 43250688. Its totient is φ = 9445248.

The previous prime is 21247063. The next prime is 21247069. The reversal of 21247065 is 56074212.

It is not a de Polignac number, because 21247065 - 2¹ = 21247063 is a prime.

It is a super-2 number, since 2×21247065² = 902875542228450, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21247063) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 10744 + ... + 12566.

It is an arithmetic number, because the mean of its divisors is an integer number (901056).

Almost surely, 2^21247065 is an apocalyptic number.

It is an amenable number.

21247065 is an abundant number, since it is smaller than the sum of its proper divisors (22003623).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21247065 is a wasteful number, since it uses less digits than its factorization.

21247065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1878 (or 1875 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 21247065 is about 4609.4538722066. The cubic root of 21247065 is about 276.9701601745.

The spelling of 21247065 in words is "twenty-one million, two hundred forty-seven thousand, sixty-five".